title: Kinetic studies of three different molecular forms of urokinase for the activation of native human plasminogen.
abstract: The kinetic parameters of three different molecular forms of urokinase (UK) for the activation of native Glu-plasminogen were compared. The apparent Michaelis constant (Km. app.) of each UK was almost of the same order of magnitude (31-38 microM), but the catalytic constants (kc) were observed to be different: UKh (high molecular weight form, molecular weight 53,000), 2.4 +/- 0.2 s-1; UK+ (low molecular weight form, molecular weight 33,000), 0.83 +/- o.10 s-1, and UKl (trypsin-digested form, molecular weight 36,000), 0.91 +/- 0.18 s-1. The overall second order rate constant, kc/Km calculated for UKh was 7.7 X 10(4) M-1 s-1, higher than for UKl (2.2 X 10(4) M-1 s-1) or UKt (2.4 X 10(4) M-1 s-1), indicating the possibility of a much higher degree of enzymatic specificity and efficiency.
mesh_terms: D010450:Endopeptidases / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008239:Lysine / Q000378:metabolism; D008970:Molecular Weight; D010446:Peptide Fragments; D010958:Plasminogen / Q000378:metabolism; D010960:Plasminogen Activators / Q000494:pharmacology; D014568:Urokinase-Type Plasminogen Activator / Q000494:pharmacology*
chemical_list: D010446:Peptide Fragments; C018998:lysyl-plasminogen; D010958:Plasminogen; D010450:Endopeptidases; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator; D008239:Lysine